Mercruiser 140 Choke Question

[lmorefield41]

I finally started the engine today after a few failed tries, broke down and rebuilt the carb with the help of my brother-in-law, and it fired right up after the rebuild and cleaning. What we couldn't figure out is why the choke was wide open as soon as we plugged the connectors up. There is some kind of electrical thermostat. Can anyone tell me the purpose of this thermostat and the correct function of it? I thought the choke flap was supposed to be closed until the engine warmed up. This choke flap was wide open before the start, and after the engine ran for 20 minutes. Didn't budge. When we hooked put the carb back on, hooked the electrical up, and turned the key, not to start, just to shoot 12V to the thermostat, it started slowly opening. Thanks in advance.

 

[lmorefield41]

Re: Mercruiser 140 Choke Question

The engine is a 1985 Mercruiser 140hp 3.0L. It's the electrical thermostat, not the vacuum.

 

[ziggy]

Re: Mercruiser 140 Choke Question

generally speaking.
weather a elec. choke or a stove pipe type like i got.
heat from either the elec. or the rising heat of a stove pipe warms up a bi metal strip . as warmed, this bi metal strips contract and wind up, thus pulling the choke plate open. a warm engine and this bi metal strip is already warmed and winding up, thus opening the choke plate.
only when the bi metal strip is cold from no 12v or no stove pipe heat does the bi metal strip act as a spring and spring load the choke plate shut. that's why ya pump the throttle once wot on a cold start. there's linkage on the carb that allows the spring to release and pull the choke plate shut.
as it warms(the bi metal strip) it pulls the choke plate open..

best i can do for an explanation....

check out s/m #10 from here. sec. 5-c7. it explains your mercarb choke operation.

 

[lmorefield41]

Re: Mercruiser 140 Choke Question

Sounds like it's working properly then. I appreciate it.